Case Study of a Hailstorm in Colorado. Part II: Particle Growth Processes at Mid-Levels Deduced from in-situ Measurements

Abstract

The microphysical, thermodynamic and vertical air motion characteristics of a hailstorm which occurred in northeast Colorado were investigated through penetrations by the T-28 research aircraft. On the basis of these measurements, the structure and composition of the regions of the strongest updrafts, the peripheral updraft and downdraft regions, and the quiescent regions of the storm were estimated. Several general aspects of the hydrometeor development processes operating within the storm were deduced from these measurements. The particle habits and sizes at any location within the storm depended primarily upon their position relative to the main updraft core. A region which extended around the forward portion of the storm was found to be an environment in which ice particles could grow rapidly through aggregation so that they were subsequently in a position to serve as graupel and hail embryos. Particles grew most rapidly along the boundaries of the WER, because the depletion of the liquid water by particle growth and by entrainment were lowest in these regions. Secondary ice particle production, evidently through an ice crystal collisional-breakup mechanism, is discussed.